SSP usually refers to single stroke pneumatic, where the air is compressed by one stroke of an integral pump lever and released by the firing valve. This differs from a gas ram where compressed gas acts as a spring and sends a piston forward to compress the air actually used to fire the pellet. SSP would not be classed as springer, piston or recoiling.
There are very few SSP rifles suitable for FT/HFT. The vast majority are match rifles for 10M shooting.